I did not know about this (and maybe people here do, but i remember the question coming up here not too long ago), but carefully applied 10% ammonia can recover a lot of the normal look of compound eyes and other features in dried insects. See the work of André De Kesel

I mixed an ammonia solution by diluting household ammonia per Andre's recommendations (50-50 household ammonia- deionized water mix) and applied it to the head area of a small dolichopodidae (long legged fly) from my bone yard. I used a small watercolor paintbrush. I was impressed with how quickly more lifelike eye appearance was restored. The color of the ommatidia immediately went from brown to green and under magnification the alternating stripes of ommatidia colors reappeared. Since the mixture was only applied to the head of this small fly, the wings were unaffected. Perhaps with more patience (subsequent applications of some water to allow the eye to rehydrate more thoroughly) an even better result might be expected.